Nonendometrioid endometrial carcinomas

Clinicopathologic studies support a classification of endometrial carcinoma into two main categories (type I and type II). Type I cancers consist of endometrioid and mucinous carcinomas, with the former being the most common, whereas serous and clear cell carcinomas are the so-called “prototype” of type II cancers. Nonendometrioid carcinomas account for approximately 10% of endometrial carcinomas and differ from endometrioid carcinomas in terms of patient demographics, morphologic features, and biological behavior. Molecular studies have provided further insights into the differing alterations involved in the development and progression of these tumors. This review summarizes the characteristic clinical, morphologic, immunophenotypic, and molecular features of the various subtypes of nonendometrioid carcinomas and also highlights relevant conditions (both nonneoplastic and neoplastic) that should be considered in the differential diagnosis of these tumors.